This is one of the back pieces. To the left is the center back seam, to the right is the side seam. So I have a total of 8 pieces about this size to bead - no problem right?! :P
Oh that is hard as I'm so bad at tracking exact yardages. For an my last Regency gown (the the Lizzie gown
), which had a very full back, I used two panels of fabric for the skirt(so 2x54") times the "waist" to floor measurement (in my case 48" in front, 5-6" longer in back for a sweep). The bodice and sleeves were probably a little over a yard, say 1.5 yd? If you are looking at more of a shaped skirt (with shaped panels rather than striaght that I tend to use) I would look up the basic S&S pattern - that should help with those yardage estimates.
The open robe is less, as there is less fabric in the skirt and bodice. How much is of course depending on your size of train o'doom. :> Hope that helps!